Igniter failure detection assemblies for furnaces, and corresponding methods of detecting igniter failure

ABSTRACT

Exemplary embodiments are provided of igniter failure detection assemblies for furnaces. In an exemplary embodiment, an igniter failure detection assembly includes a hot surface igniter, an igniter relay coupled to the hot surface igniter, a resistor coupled in parallel with the hot surface igniter and defining a node between the igniter relay, the resistor and hot surface igniter, and a controller configured to detect a voltage at the node and determine whether a fault condition of the hot surface igniter exists based on the detected voltage at the node. A detected node voltage corresponding to a normal operation resistance value of the hot surface igniter is indicative of a normal operating hot surface igniter, and a detected node voltage corresponding to a resistance value of the resistor is indicative of a fault condition of the hot surface igniter. Example methods of detecting an igniter fault condition are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit and priority of Indian Patent Application No. 201721014345 filed Apr. 22, 2017. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure generally relates to igniter failure detection assemblies for furnaces, and corresponding methods of detecting igniter failure.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Furnaces often include an igniter which heats up based on a supplied current to ignite a combustible gas of the furnace. Igniter relays are typically used to supply current to the igniter. Furnaces also typically include a flame sensor to detect the presence or absence of a flame.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a block diagram of an igniter failure detection assembly according to one exemplary embodiment of the present disclosure;

FIG. 2 is a block diagram of an igniter failure detection assembly of FIG. 1, including a flame sensor;

FIG. 3 is a circuit diagram of an igniter failure detection assembly according to another exemplary embodiment of the present disclosure; and

FIG. 4 is a chart of example voltage conditions of the igniter failure detection assembly of FIG. 3.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

As recognized herein, hot surface igniters (e.g., electric resistance igniters, etc.) in HVAC systems are often used to ignite combustible gas in a furnace of the HVAC system. The hot surface igniter is powered by a voltage supplied from a power source (e.g., a 110 VAC supply, etc.) via an electromechanical switch call relay (e.g., an igniter relay, etc.). During operation, the hot surface igniter could become damaged and fail to heat up (e.g., ignite, etc.) the combustible gas of the furnace. Separately, the igniter relay has a limited lifespan and the igniter relay could fail to open or close. Existing systems are not capable of detecting failures (e.g., fault conditions, etc.) of the hot surface igniter.

As also recognized herein, adding a resistance (e.g., high value resistor, etc.) in parallel with the hot surface igniter allows for detection of fault conditions of the hot surface igniter. For example, when the hot surface igniter is working properly, the effective resistance of the parallel resistor and hot surface igniter will be low (e.g., will correspond to a resistance of the hot surface igniter, etc.). When the hot surface igniter is damaged (e.g., has a fault condition, etc.), the effective resistance of the parallel resistor and hot surface igniter would become high (e.g., correspond to a resistance value of the resistor, etc.). This change in resistance could be detected by a controller, etc., to separate detection of hot surface igniter faults and igniter relay faults.

Exemplary embodiments are provided of igniter failure detection assemblies for a furnace. FIG. 1 illustrates an exemplary embodiment of an igniter failure detection assembly 100 having a hot surface igniter 102. The hot surface igniter 102 is adapted to, in response to receiving a current, heat up to ignite a combustible gas of the furnace.

The hot surface igniter 102 may include any suitable resistive igniter, etc., and is adapted to ignite the combustible gas of the furnace via heat when the hot surface igniter 102 is supplied with a current. For example, during normal operation, the hot surface igniter 102 may be turned on, etc., to start, initiate, etc., a combustion process of the furnace (e.g., in response to a thermostat call for heat, etc.).

The igniter failure detection assembly 100 also includes an igniter relay 104 (e.g., an igniter drive relay 104, etc.) coupled to the hot surface igniter 102. The igniter relay 104 is adapted to selectively supply a current to the hot surface igniter 102 based on a state of the igniter relay 104.

For example, as illustrated in FIG. 1, the igniter relay 104 is coupled between a voltage source 105 and the hot surface igniter 102. The voltage source 105 may include any suitable source for supplying voltage and/or current to the hot surface igniter 102, including but not limited to, a power supply, a line voltage input, a utility grid voltage supply, etc. For example, in some embodiments, the voltage source 105 may include about a 110 volt alternating current (VAC) supply.

The relay 104 is selectively turned on and off (e.g., opened and closed, etc.) via a control signal, which may be provided by controller 108 in FIG. 1, may be provided by another controller (e.g., furnace controller, thermostat, etc.) which is not shown in FIG. 1, etc. For example, the relay 104 may be turned on (e.g., closed, etc.) in response to a call for initiation or startup of a combustion process of the furnace (e.g., a call for heat, etc.), where the relay 104 starts to supply current and/or voltage from the voltage source 105 to the hot surface igniter 102. The relay 104 may include any suitable relay element, switch element, etc., capable of selectively providing current from the voltage source 105 to the hot surface igniter 102.

As shown in FIG. 1, a resistor 106 is coupled in parallel with the hot surface igniter 102. Thus, a node 110 is defined between the igniter relay 104, the hot surface igniter 102 and the resistor 106. As mentioned above, the resistor 106, coupled in parallel with the hot surface igniter 102, allows for detection of fault conditions of the hot surface igniter 102. For example, a resistance value of the resistor 106 may be sufficiently greater than a resistance value of the hot surface igniter 102 during normal operation. Therefore, when the hot surface igniter 102 is operating properly (e.g., a normal operating condition of the hot surface igniter, etc.), an equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102 may correspond to the resistance of the hot surface igniter 102 during normal operation, because the normal operating resistance of the hot surface igniter 102 is sufficiently less than the resistance value of the resistor 106.

In some embodiments, the resistance of the hot surface igniter 102 during normal operating conditions may be less than about fifty ohms (e.g., about thirty ohms, etc.), and a resistance value of the resistor 106 may be more than about fifty ohms (e.g., about 500 k ohms, etc.). As should be apparent, these resistance values are provided as only one example, and other embodiments may use any other suitable resistance values sufficient to distinguish resistance of the resistor 106 from resistance of the hot surface igniter 102 during normal operation, etc.

As described above, when the hot surface igniter 102 is operating properly the equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102 will correspond to a resistance value of the hot surface igniter 102 during normal operation (e.g., about thirty ohms, etc.). In contrast, during a fault condition of the hot surface igniter 102 (e.g., where the hot surface igniter 102 is not operating properly, is not turning on, etc.) the equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102 will correspond to the resistance value of the resistor 106. This is due to the fact that a faulty hot surface igniter 102 may have an approximately infinite resistance (e.g., open circuit, resistance value that is much higher than the resistance value of resistor 106, etc.).

Therefore, detection of the equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102 allows for determination of whether the hot surface igniter 102 has failed (e.g., is experiencing a fault condition, etc.). As shown in FIG. 1, a controller 108 is coupled to the node 110 defined between the igniter relay 104, the resistor 106 and the hot surface igniter 102.

The controller 108 is configured to detect a voltage at the node 110 to determine whether a fault condition of the hot surface igniter 102 exists. For example, the voltage at node 110 may correspond to the equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102. Therefore, when the detected node voltage corresponds to a normal operation resistance value of the hot surface igniter 102 (e.g., less than about fifty ohms, about thirty ohms, etc.), the detected node voltage is indicative of a normal operating hot surface igniter. In contrast, when the detected node voltage corresponds to a resistance value of the resistor 106 (e.g., more than about fifty ohms, about 500 k ohms, etc.), the detected node voltage is indicative of a fault condition of the hot surface igniter 102.

The controller 108 may be configured to perform operations using any suitable combination of hardware and software. For example, the controller 108 may include any suitable circuitry, logic gates, microprocessor(s), computer-executable instructions stored in memory, etc., operable to cause the controller 108 to perform actions described herein (e.g., determining fault conditions of the hot surface igniter 102, etc.)

As should be apparent, a correspondence relationship between the detected voltage at node 110 and the equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102 may be determined based on values, parameters, etc., of the components coupled in the igniter failure detection assembly 100. For example, a low voltage value at node 110 may correspond to low equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102 (e.g., indicative of normal operation of hot surface igniter 102, etc.). A high voltage value at node 110 may correspond to high equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102 (e.g., indicative of a fault condition of the hot surface igniter 102, etc.). As should be apparent, a high voltage value, a low voltage value, etc., at node 110 may be determined based on resistances of components coupled to node 110 in the igniter failure detection assembly 100. In some embodiments, the components may be coupled such that a low voltage value at node 110 is indicative of a high equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102, a high voltage value at node 110 is indicative of a low equivalent resistance of the parallel-coupled resistor 106 and the hot surface igniter 102, etc.

FIG. 2 illustrates another exemplary embodiment of an igniter failure detection assembly 200. The igniter failure detection assembly 200 is similar to the assembly 100 illustrated in FIG. 1, but further includes a flame sensor 212.

The flame sensor 212 is adapted to sense a presence or absence of flame in the furnace. For example, the flame sensor 212 may detect whether combustible gas of the furnace has been properly ignited in response to initiation of a combustion process of the furnace. If the flame sensor 212 does not detect a presence of a flame generated in response to a startup, initiation, etc., of the combustion process of the furnace, the flame sensor 212 may indicate a fault condition of one of the igniter relay 104 and the hot surface igniter 102.

As shown in FIG. 2, the controller 108 is coupled to the flame sensor 212 to receive a signal indicative of the presence or absence of a flame, as detected by the flame sensor 212. The controller 108 may use the detected flame sensor signal to determine when the furnace is operating properly. For example, if the controller 108 detects an absence of a flame via the flame sensor 212 after a combustion process of the furnace has been initiated, the controller 108 may detect a voltage at node 110 to determine which component(s) of the igniter failure detection assembly 100 are experiencing a fault condition (e.g., the igniter relay 104, the hot surface igniter 102, etc.).

When the controller 108 detects an absence of a flame and the detected node voltage corresponds to the normal operation resistance value of the hot surface igniter 102, the controller 108 may determine a fault condition of the igniter relay 104. When the controller 108 detects an absence of a flame and the detected node voltage corresponds to the resistance value of the hot surface igniter 102, the controller 108 may determine a fault condition of the hot surface igniter 102.

FIG. 3 illustrates another exemplary embodiment of an igniter failure detection assembly 300. Similar to the assemblies 100, 200 of FIGS. 1 and 2, the igniter failure detection assembly 300 includes a hot surface igniter 302 coupled in parallel with a resistor 306. An igniter relay 304 is coupled to the hot surface igniter 302 to provide a current to the hot surface igniter 302. For example, when the inducer relay 314 (e.g., an inducer drive relay, etc.) is in a closed state and the igniter relay 304 is in a closed state, the igniter relay 304 may supply current to the hot surface igniter 302 from the 110 VAC line voltage input.

As shown in FIG. 3, the igniter failure detection assembly 300 also includes an inducer relay 314 coupled between the 110 VAC line voltage input and the igniter relay 304. The inducer relay 314 may be adapted to provide the 110 VAC line voltage input to igniter relay 304 and an inducer (not shown) of the furnace to operate the inducer, etc.

The igniter failure detection assembly 300 also includes another resistor 316 coupled in parallel with the igniter relay 304. The resistor 316 may have a resistance value that is substantially the same as the resistance value of the resistor 306 coupled in parallel with the hot surface igniter 302.

As shown in FIG. 3, a node 310 is defined between the igniter relay 304, the resistor 316, the hot surface igniter 302 and the resistor 306. The node 310 is coupled to a microcontroller (not shown) via resistors R3 and R4. This allows the microcontroller to detect a voltage at node 310 to determine a fault condition of the igniter relay 304, the hot surface igniter 302, etc.

For example, when the inducer relay 314 and the igniter relay 304 are both on and the hot surface igniter 302 is operating normally, a voltage at node 310 would be approximately equal to the line voltage. During a warm-up period of the hot surface igniter 302, the inducer relay 314 and the igniter relay 304 are both turned on, and the hot surface igniter 302 is initially off.

The igniter relay 304 is turned off (e.g., in an off-state, etc.) when the hot surface igniter 302 is required to be off (e.g., no current call for hot surface igniter 302 operation, etc.). The igniter relay 304 is turned on (e.g., in an on-state, etc.) when the hot surface igniter 302 is required to be on (e.g., a call for hot surface igniter 302 operation, etc.). The voltage at node 310 and the call status (e.g., on or off software status, control signal, etc.) for igniter relay 304 are used to identify whether the hot surface igniter 302 is faulty and/or the igniter relay 304 is faulty.

In some embodiments, the voltage at node 310 may have one of at least three discrete values (e.g., approximately equal to the line voltage, approximately equal to half of the line voltage, and approximately equal to zero). FIG. 4 includes a chart 400 illustrating example voltages at node 310 during both an igniter relay on-state and an igniter relay off-state, and the fault conditions indicated by the respective node voltages.

When the inducer relay 314 is on and the igniter relay 304 is set to off by the controller, the voltage at node 310 should be approximately zero volts. As shown in FIG. 4, if the controller detects a voltage at node 310 of approximately zero volts when the inducer relay 314 is on and the igniter relay 304 is set to off, the controller may determine that no fault condition exists. Therefore, igniter relay 304 and hot surface igniter 302 may be operating in normal (e.g., healthy, etc.) conditions (e.g., a hot surface igniter resistance of approximately thirty ohms, etc.).

If the controller detects a voltage at node 310 of approximately half of the line voltage (i.e., LV/2) when the inducer relay 314 is on and the igniter relay 304 is set to off by the controller, the controller may determine that the hot surface igniter 302 is faulty (e.g., is open, has a fault condition, etc.).

If the controller detects a voltage at node 310 approximately equal to the line voltage (i.e., LV) when the inducer relay 314 is on and the igniter relay 304 is set to off by the controller, the controller may determine that the igniter relay 304 is stuck in a closed state, experiencing a fault condition, etc. For example, no change in feedback voltage from node 310 when the igniter relay status is set to off may indicate the igniter relay 304 is stuck in a closed state.

As shown in FIG. 4, when the inducer relay 314 is on and the igniter relay 304 is set from the off-state to the on-state by the controller, if the voltage at node 310 is approximately equal to the line voltage (e.g., LV) the controller may not be able to identify a fault related to the igniter relay 304 and the hot surface igniter 302.

If the controller detects a voltage at node 310 of approximately half of the line voltage (i.e., LV/2) when the inducer relay 314 is on and the igniter relay 304 status is set from off to on by the controller, the controller may determine that the igniter relay 304 is faulty (e.g., stuck in an open position, etc.) and the hot surface igniter 302 is faulty (e.g., is open, has a fault condition, etc.). If the igniter relay 304 is turned on without a fault, the voltage at node 310 should be approximately equal to the line voltage.

If the controller detects a voltage at node 310 of approximately zero volts when the inducer relay 314 is on and the igniter relay 304 status is set from off to on by the controller, the controller may determine that the igniter relay 304 is faulty (e.g., is open, has a fault condition, etc.). For example, no change in feedback voltage from node 310 when the igniter relay status is set from on to off may indicate the igniter relay 304 is stuck in a closed state. As above, if the igniter relay 304 is turned on without a fault, the voltage at node 310 should be approximately equal to the line voltage.

The voltage at node 310 will be determined based on the resistance value of resistor 306, and a resistance value of the hot surface igniter 302. As mentioned above, the hot surface igniter 302 may have an approximately infinite resistance (e.g., open circuit, etc.) during a fault condition of the hot surface igniter 302, and may have a low resistance value (e.g., less than about fifty ohms, about thirty ohms, about fifteen ohms, etc.) when the hot surface igniter 302 is working properly.

The voltage at node 310 is fed to a microcontroller, optionally via a conditioning circuit (e.g., resistors, etc.), that may adjust the voltage signal within a range suitable for the microcontroller input.

When the igniter relay 304 is stuck in an open position, voltage at node 310 would be the same as if the igniter relay 304 were purposefully turned off. If the igniter relay 304 is stuck in a closed position, voltage at node 310 would be the same as if the igniter relay 304 were purposefully turned on. This allows determination of the correct fault detection while operating the igniter relay 304.

The example igniter fault detection assemblies described herein may be included in any suitable HVAC system, etc. The igniter fault detection assemblies described herein may be part of a furnace of the HVAC system. In some embodiments, the controllers described herein may be furnace controllers, thermostats, etc.

According to another example embodiment of the present disclosure, a method of detecting a fault condition of a furnace igniter assembly is disclosed. The furnace igniter assembly includes a hot surface igniter adapted to heat up to ignite a combustible gas of the furnace, an igniter relay coupled to the hot surface igniter to selectively supply a current to the hot surface igniter based on a state of the igniter relay, and a resistor coupled in parallel with the hot surface igniter and defining a node between the igniter relay, the resistor and the hot surface igniter. The exemplary method includes initiating a combustion process of the furnace, and detecting a voltage at the node defined between the igniter relay, the resistor and the hot surface igniter. The method further includes determining whether a fault condition of the hot surface igniter exists based on the detected voltage at the node, wherein a detected node voltage corresponding to a normal operation resistance value of the hot surface igniter is indicative of a normal operating hot surface igniter, and a detected node voltage corresponding to a resistance value of the resistor is indicative of a fault condition of the hot surface igniter.

In some embodiments, the method includes sensing a presence or absence of a flame generated in response to ignition of the combustible gas by the hot surface igniter and determining whether the fault condition of the hot surface igniter exists in response to detection of the absence of a flame after the start of the combustion process of the furnace.

The method may include, when an absence of a flame is detected after the start of the combustion process of the furnace and the detected node voltage corresponds to the normal operation resistance value of the hot surface igniter, determining that a fault condition of the igniter relay exists. The resistance value of the hot surface igniter is less than about fifty ohms and the resistance value of the resistor is greater than about fifty ohms.

In some embodiments, the furnace igniter assembly further includes an inducer relay coupled to the igniter relay and a second resistor coupled in parallel with the igniter relay, and the second resistor has a resistance value that is substantially the same as the resistance value of the resistor coupled in parallel with the hot surface igniter. In those cases, the method may include determining whether a fault condition of the igniter relay exists based on the detected node voltage of the node defined between the hot surface igniter and the igniter relay.

In some embodiments, a temperature sensor may be used to check whether a hot surface igniter is heating properly before determining the hot surface igniter is faulty. Alternatively, or in addition, a current of the hot surface igniter could be measured to check whether the hot surface igniter is operating properly before determining the hot surface igniter is faulty.

Example embodiments described herein may allow furnace control boards, etc., to detect whether a hot surface igniter is faulty or whether an igniter relay is faulty. This may allow a technician to determine whether a control board should be replaced, or whether only the hot surface igniter needs to be replaced. This may allow for reduced repair time, reduced repair cost, etc.

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “includes,” “including,” “has,” “have,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

The term “about” when applied to values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters. For example, the terms “generally”, “about”, and “substantially” may be used herein to mean within manufacturing tolerances.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements, intended or stated uses, or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. An igniter failure detection assembly for a furnace, the igniter failure detection assembly comprising: a hot surface igniter adapted to, in response to receiving a current, heat up to ignite a combustible gas of the furnace; an igniter relay coupled to the hot surface igniter, the igniter relay adapted to selectively supply a current to the hot surface igniter based on a state of the igniter relay; a resistor coupled in parallel with the hot surface igniter and defining a node between the igniter relay, the resistor, and the hot surface igniter; and a controller configured to detect a voltage at the node and determine whether a fault condition of the hot surface igniter exists based on the detected voltage at the node, wherein a detected node voltage corresponding to a normal operation resistance value of the hot surface igniter is indicative of a normal operating hot surface igniter, and a detected node voltage corresponding to a resistance value of the resistor is indicative of a fault condition of the hot surface igniter.
 2. The igniter failure detection assembly of claim 1, further comprising a flame sensor adapted to sense a presence or absence of a flame generated in response to ignition of the combustible gas by the hot surface igniter.
 3. The igniter failure detection assembly of claim 2, wherein the controller is coupled to the flame sensor and is configured to detect the presence or absence of a flame via the flame sensor.
 4. The igniter failure detection assembly of claim 3, wherein the controller is configured to determine whether the fault condition of the hot surface igniter exists in response to detection of the absence of a flame after the start of a combustion process of the furnace.
 5. The igniter failure detection assembly of claim 4, wherein the controller is configured to, when the controller detects an absence of a flame and the detected node voltage corresponds to the normal operation resistance value of the hot surface igniter, determine a fault condition of the igniter relay.
 6. The igniter failure detection assembly of claim 1, wherein the resistance value of the hot surface igniter is less than about fifty ohms.
 7. The igniter failure detection assembly of claim 1, wherein the resistance value of the resistor is greater than about fifty ohms.
 8. The igniter failure detection assembly of claim 7, wherein the resistance value of the resistor is greater than or equal to about 500 thousand ohms.
 9. The igniter failure detection assembly of claim 1, wherein the igniter relay is coupled to a line voltage input and is adapted to selectively supply the line voltage input to the hot surface igniter based on the state of the igniter relay.
 10. The igniter failure detection assembly of claim 9, wherein the line voltage input is approximately 110 volts alternating current (VAC).
 11. The igniter failure detection assembly of claim 9, further comprising: an inducer relay coupled between the line voltage input and the igniter relay; and a second resistor coupled in parallel with the igniter relay, the second resistor having a substantially similar resistance value as the resistor coupled in parallel with the hot surface igniter.
 12. The igniter failure detection assembly of claim 11, wherein, when a status of the igniter relay is set to off, the controller is configured to: when the detected node voltage is equal to about half of the line voltage input, determine a fault condition of the hot surface igniter; when the detected node voltage is about equal to the line voltage input, determine the igniter relay is stuck in a closed position; and when the detected node voltage is about zero, determine a normal operation condition of the hot surface igniter and the igniter relay.
 13. The igniter failure detection assembly of claim 11, wherein, when a status of the igniter relay is set to on, the controller is configured to: when the detected node voltage is equal to about half of the line voltage input, determine a fault condition of the hot surface igniter and that the igniter relay is stuck in an open position; and when the detected node voltage is about zero, determine the igniter relay is stuck in an open position.
 14. The igniter failure detection assembly of claim 1, further comprising a conditioning circuit coupled between the node and the controller to adjust the detected node voltage within a range suitable for the microcontroller input.
 15. An HVAC system including a furnace having the igniter failure detection assembly of claim 1, wherein the controller comprises a furnace controller of the furnace.
 16. A method of detecting a fault condition of a furnace igniter assembly, the furnace igniter assembly including a hot surface igniter adapted to heat up to ignite a combustible gas of the furnace, an igniter relay coupled to the hot surface igniter to selectively supply a current to the hot surface igniter based on a state of the igniter relay, and a resistor coupled in parallel with the hot surface igniter and defining a node between the igniter relay, the resistor and the hot surface igniter, the method comprising: initiating a combustion process of the furnace; detecting a voltage at the node defined between the igniter relay, the resistor and the hot surface igniter; and determining whether a fault condition of the hot surface igniter exists based on the detected voltage at the node, wherein a detected node voltage corresponding to a normal operation resistance value of the hot surface igniter is indicative of a normal operating hot surface igniter, and a detected node voltage corresponding to a resistance value of the resistor is indicative of a fault condition of the hot surface igniter.
 17. The method of claim 16, further comprising sensing a presence or absence of a flame generated in response to ignition of the combustible gas by the hot surface igniter, and determining whether the fault condition of the hot surface igniter exists in response to detection of the absence of a flame after the start of the combustion process of the furnace.
 18. The method of claim 17, further comprising, when an absence of a flame is detected after the start of the combustion process of the furnace and the detected node voltage corresponds to the normal operation resistance value of the hot surface igniter, determining that a fault condition of the igniter relay exists.
 19. The method of claim 16, wherein the resistance value of the hot surface igniter is less than about fifty ohms and the resistance value of the resistor is greater than about fifty ohms.
 20. The method of claim 16, wherein the furnace igniter assembly further includes an inducer relay coupled to the igniter relay and a second resistor coupled in parallel with the igniter relay, and the second resistor has a resistance value that is substantially the same as the resistance value of the resistor coupled in parallel with the hot surface igniter, the method further comprising: determining whether a fault condition of the igniter relay exists based on the detected node voltage of the node defined between the hot surface igniter and the igniter relay. 